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Use try/catch to detect undefined globals for canvas

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This commit is contained in:
Don Mitchell
2012-10-31 17:29:19 -04:00
parent 6bbe82b697
commit 2b5e55b662
1 changed files with 68 additions and 59 deletions
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127
common/lib/xmodule/xmodule/js/src/capa/schematic.js
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@@ -3339,23 +3339,28 @@ schematic = (function() {
}
// add method to canvas to compute relative coords for event
if (HTMLCanvasElement) HTMLCanvasElement.prototype.relMouseCoords = function(event){
// run up the DOM tree to figure out coords for top,left of canvas
var totalOffsetX = 0;
var totalOffsetY = 0;
var currentElement = this;
do {
totalOffsetX += currentElement.offsetLeft;
totalOffsetY += currentElement.offsetTop;
}
while (currentElement = currentElement.offsetParent);
// now compute relative position of click within the canvas
this.mouse_x = event.pageX - totalOffsetX;
this.mouse_y = event.pageY - totalOffsetY;
this.page_x = event.pageX;
this.page_y = event.pageY;
try {
if (HTMLCanvasElement)
HTMLCanvasElement.prototype.relMouseCoords = function(event){
// run up the DOM tree to figure out coords for top,left of canvas
var totalOffsetX = 0;
var totalOffsetY = 0;
var currentElement = this;
do {
totalOffsetX += currentElement.offsetLeft;
totalOffsetY += currentElement.offsetTop;
}
while (currentElement = currentElement.offsetParent);
// now compute relative position of click within the canvas
this.mouse_x = event.pageX - totalOffsetX;
this.mouse_y = event.pageY - totalOffsetY;
this.page_x = event.pageX;
this.page_y = event.pageY;
}
}
catch (err) { // ignore
}
///////////////////////////////////////////////////////////////////////////////
@@ -4091,48 +4096,52 @@ schematic = (function() {
// add dashed lines!
// from http://davidowens.wordpress.com/2010/09/07/html-5-canvas-and-dashed-lines/
CanvasRenderingContext2D.prototype.dashedLineTo = function(fromX, fromY, toX, toY, pattern) {
// Our growth rate for our line can be one of the following:
// (+,+), (+,-), (-,+), (-,-)
// Because of this, our algorithm needs to understand if the x-coord and
// y-coord should be getting smaller or larger and properly cap the values
// based on (x,y).
var lt = function (a, b) { return a <= b; };
var gt = function (a, b) { return a >= b; };
var capmin = function (a, b) { return Math.min(a, b); };
var capmax = function (a, b) { return Math.max(a, b); };
var checkX = { thereYet: gt, cap: capmin };
var checkY = { thereYet: gt, cap: capmin };
if (fromY - toY > 0) {
checkY.thereYet = lt;
checkY.cap = capmax;
}
if (fromX - toX > 0) {
checkX.thereYet = lt;
checkX.cap = capmax;
}
this.moveTo(fromX, fromY);
var offsetX = fromX;
var offsetY = fromY;
var idx = 0, dash = true;
while (!(checkX.thereYet(offsetX, toX) && checkY.thereYet(offsetY, toY))) {
var ang = Math.atan2(toY - fromY, toX - fromX);
var len = pattern[idx];
offsetX = checkX.cap(toX, offsetX + (Math.cos(ang) * len));
offsetY = checkY.cap(toY, offsetY + (Math.sin(ang) * len));
if (dash) this.lineTo(offsetX, offsetY);
else this.moveTo(offsetX, offsetY);
idx = (idx + 1) % pattern.length;
dash = !dash;
}
};
try {
if (CanvasRenderingContext2D)
CanvasRenderingContext2D.prototype.dashedLineTo = function(fromX, fromY, toX, toY, pattern) {
// Our growth rate for our line can be one of the following:
// (+,+), (+,-), (-,+), (-,-)
// Because of this, our algorithm needs to understand if the x-coord and
// y-coord should be getting smaller or larger and properly cap the values
// based on (x,y).
var lt = function (a, b) { return a <= b; };
var gt = function (a, b) { return a >= b; };
var capmin = function (a, b) { return Math.min(a, b); };
var capmax = function (a, b) { return Math.max(a, b); };
var checkX = { thereYet: gt, cap: capmin };
var checkY = { thereYet: gt, cap: capmin };
if (fromY - toY > 0) {
checkY.thereYet = lt;
checkY.cap = capmax;
}
if (fromX - toX > 0) {
checkX.thereYet = lt;
checkX.cap = capmax;
}
this.moveTo(fromX, fromY);
var offsetX = fromX;
var offsetY = fromY;
var idx = 0, dash = true;
while (!(checkX.thereYet(offsetX, toX) && checkY.thereYet(offsetY, toY))) {
var ang = Math.atan2(toY - fromY, toX - fromX);
var len = pattern[idx];
offsetX = checkX.cap(toX, offsetX + (Math.cos(ang) * len));
offsetY = checkY.cap(toY, offsetY + (Math.sin(ang) * len));
if (dash) this.lineTo(offsetX, offsetY);
else this.moveTo(offsetX, offsetY);
idx = (idx + 1) % pattern.length;
dash = !dash;
}
};
}
catch (err) { //noop
}
// given a range of values, return a new range [vmin',vmax'] where the limits
// have been chosen "nicely". Taken from matplotlib.ticker.LinearLocator
function view_limits(vmin,vmax) {